WASM_X64: Support printing integers

[Shaikh-Ubaid]

Example:

def Main0():
    x: i32
    x = (2+3)* (-5)
    y: i32 = 100
    z: i32 = 2147483647
    w: i32 = -2147483648
    print(x)
    print(y)
    print(z)
    print(w)
    print("Hi")
    print("Hello")
    print((5-2) * 7)
    print("Bye")

Main0()

Binary Output:

(lp) lpython$ lpython integration_tests/print_03.py  --backend wasm_x64 -o tmp
(lp) lpython$ ./tmp
-25
100
2147483647
-2147483648
Hi
Hello
21
Bye
(lp) lpython$ 

Text Format Output:

(wasm_asm) lpython$ nasm -fbin ./main.asm && chmod +x main && ./main
-25
100
2147483647
-2147483648
Hi
Hello
21
Bye
(wasm_asm) lpython$ 

[Shaikh-Ubaid]

This is ready. Please possibly review and please share feedback.

[certik]

After this is merged, let's document what the "calling convention" is. It looks like the caller is responsible to put arguments on stack, as well as removing them from stack once the called function (print_i64 in this case) finishes?

[Shaikh-Ubaid]

Yes, the caller is responsible to put arguments on stack.

In wasm, the arguments are used up by the called function (that is there is no need to explicitly remove them).

In assembly x86 and/or x64, we are currently manually/explicitly removing the passed arguments in the visit_Call() function:

lpython/src/libasr/codegen/wasm_to_x64.cpp

Lines 97 to 123 in 7aaedcc

	void visit_Call(uint32_t func_idx) {
	if (func_idx <= 6U) {
	call_imported_function(func_idx);
	return;
	}
	func_idx -= 7u; // adjust function index as per imports
	m_a.asm_call_label(exports[func_idx].name);
	// Pop the passed function arguments
	wasm::FuncType func_type = func_types[type_indices[func_idx]];
	for (uint32_t i = 0; i < func_type.param_types.size(); i++) {
	m_a.asm_pop_r64(X64Reg::rax);
	}
	// Adjust the return values of the called function
	X64Reg base = X64Reg::rsp;
	for (uint32_t i = 0; i < func_type.result_types.size(); i++) {
	// take value into eax
	m_a.asm_mov_r64_m64(X64Reg::rax, &base, nullptr, 1,
	-8 * (func_type.param_types.size() + 2 +
	codes[func_idx].locals.size() + 1));
	// push eax value onto stack
	m_a.asm_push_r64(X64Reg::rax);
	}
	}

[Shaikh-Ubaid]

For the print_i64, as it is an imported function and as this is an initial support, we are removing the passed arguments just after the call:

lpython/src/libasr/codegen/wasm_to_x64.cpp

Lines 50 to 56 in 7aaedcc

	void call_imported_function(uint32_t func_idx) {
	switch (func_idx) {
	case 0: { // print_i32
	m_a.asm_call_label("print_i64");
	m_a.asm_pop_r64(X64Reg::r15); // pop the passed argument
	break;
	}

[certik]

I think we should follow the WASM convention and the function should remove them, so in this case print_i64 should remove the arguments from stack. What do you think?

I opened up an issue so that we do not forget: #1381

[certik]

I think this looks great! Thanks for this.

[Shaikh-Ubaid]

Thank you for the approval and merging.